Engineering the initial state in broadband population inversion

TL;DR

This paper introduces a geometric control method to achieve full population inversion in quantum systems with sublevel structures by preparing specific initial superpositions, overcoming traditional limitations with ultrafast pulses.

Contribution

It develops a novel control strategy that manipulates initial quantum states to enable population inversion or blockade, surpassing the pulse area theorem constraints.

Findings

Population inversion achieved with minimal pulse area.

Full control over initial sublevels enhances inversion efficiency.

Method overcomes traditional pulse area limitations.

Abstract

Quantum systems with sublevel structures prevent full population inversion from one manifold of sublevels to the other using strong ultrafast resonant pulses. In this work we explain the mechanism by which this population transfer is blocked. We then develop a novel concept of geometric control, assuming full or partial coherent manipulation within the manifolds and show that by preparing specific coherent superpositions in the initial manifold, full population inversion or full population blockade, {\it i.e} laser-induced transparency, can be achieved. In particular, by parallel population transfer we show how population inversion between the manifolds can be obtained with minimal pulse area. As the number of sublevels increases, population inversion can overcome the pulse area theorem at the expense of full control over the initial manifold of sublevels.